In all the previous recipes, the data returned from the service contained all the records, and the same were displayed in the list. When working with a hierarchical data structure instead of a flat one, the ListView widget can be customized so that it can display the data in a hierarchical way, that is, displaying the elements in the first level of the hierarchy and then traversing through various levels until the leaf nodes in the hierarchy are reached.
To build a hierarchical list, the service should return data that lists the first set of records that need to be displayed. Each record should have a field that indicates whether there are child records or it's a leaf node in the hierarchy. This information will then be used in the ListView widget, which would enable the user to navigate through the hierarchy.